Means for producing a level effect



April 1935. I J. R. G. J. BLANCARD 1,996,609

mums FOR rnpnucme A LEVEL EFFECT Filed March 22, 1952 2 Sheets-Sheet 1 al ATTORNEYS l mum and/or minimum intensity mayf bemore I accurately defined by)the' receivingjapparatusi netic wave's is, bythef use ofajlbop" antenna.

the invention. 20

, mop-antenna; The intensity dia;gra1ii of@thera 355 azimuth angles"from"0''to360; such'signalsheing i a maximum when the planes-of thenloopz rioints :4 Figure ris za theoreticia-lflpolarfdiagramiin which intensity of radiation is .plottedfvectorially;

Patented Apt, 2, 1935 macro-a f PATENT oFFieE;

lli- 996,609 v ronmomma 5 never. EFFECT Jeam'TRogeicGeoi-gesw Julesl'Blancard, Meulan;

1 5 Francm.assignor;. to Americanolsothi Corp'ome tiom a corporationr ofaNew York 1 ;emanate-Ma ma-1932; swat-Nb. 600;49e

' m r ance March 23, 1931 -3 olaiins., (ol zso -i-iy he prouucea w en the received signal isfiei'ow a" certain minimum; that is, below a certain strength. Thisiis illustrated in FigmeB in'whiclr This invention pertains; generally to directed e1ectromagnetic waves, and particularly toigthereception' thereofi The invention" pertains imjore' particularlyto' means'wherebythepoints'oimaxi}' are plotted as ordinates. The curve l'l'indic'ates; a maximum. signal when} the received; signal, is between zero and a point. which for convenience One means ofsending diiebtiedijelebtro-ifiag- This isillustratedfin the'diawirigs, in which r r the strength of the resultant" signal decreases until it"is: entirely eiiminatedjat a second; point YFigure-Z isa' practical diagram ofsuch'inten's'a marked'ior'convenience B I,

Figures 314, 5 andf6are curves of operation;

Figures"? andiig alrev diegflrams. j 1 v Figure 9; is" a conventio' a1" grid-voltage mate; current curve.

mayibe considerably decreased, or entire r'i 'gure o. is a" circuitdi'agram ofonefforiri of A curve c rrespond :0 opera ion with er ceived' signal strength above a, certain strength is illustrated in Figure 5; in which receiv'edfsignalsabove the .value C cause'aresult'ant 7 signal of more or Iessconst'ant strength butwhich in strength asthe 'receivedlsignal (ii-n minishes below the. value quntil it isentirely eliminated ata point-D1 By means above alluded I "Figure- 11'isa-cirbuitdiagraih or anomr ro m r theinyention;

ff Releiring'tojFigufeliat" lllisisho'wn aisiinple 'diititiiifield beingfillusti'atedi' by the circles I r angl'f 12 which: pass through'the faces of the. coil lilflaiiid fiire tangent tothelinieginarylinePassing throughth'e center of thefaces of'coil' flri- "In: Figure li'zis'. 21* and-'21; I- I ting staition by. means of simple" 100s antenna f o IriEiguie 8fisvsho=wnan operationldiagramcoi Ir'e'sp'oii'dihgto Figure 6,. the resultant signal lieg; prioduc'ed 'when the" strength of thereceived signal isbetween the lines 23' andz l} According to this invention, the above results 7 toward" the transmitting station,- and being: a. minimum whensuchl plane'isiatrightangles to said firstimentionedlpo ti'ori;

arm emskn'own inthe, rt; suchas' al'comhina 't'ion of antenna, the intensity diagram-i may he varied considerably;onejtwell known form, being he shape of a jcardioid, The invention'hereih the'oscillator circuit; 'Inay be causecli'to oscillate when the received signal isbetween zero and a predete'ir'nined'levelYofIstrengtmbeyondwhichthe oscillations} are stop'ped A resultant signaleontrolled byjos'cillations in the oscillator; circuit wouldthu she produced when the strength ofthe is adapt'edffor'use wit li' an y such form; 1 V

In'view'of th factthatjthemaxima aiid'mfiiiina of the above niehtioned"diagrams: are notLfsuffie. ci'ently sharpfor'all-practical bur' ioses,.ithecoines desirable to periectiapparaqtus for thefpurp'ose-of eitherreceivin'g' thefmin'im'a or'the maxiina to the exclusion of the'lf rest ofjthe diagram, requires apparatuscapable of: evinci'ng a? level a 0i threshold efiect} thfiisya; determinants of. when the signals arebelow acert'ain strength or are above a v certain strength. T Aiconwvenieritiform of apparatus is one thatlwill produce a result ant signal when the received; signals are below a; certain strength sorwilla produce; ai-resultant; r alwhenxthe receivedsignalsrare above a-eertain strength-. i V

Take theicase in which a, resultant signalist'o a. predetermined level of strength, in which case theresultant signal 'woulclbe producecl'hetween the-lines 23 andi in Figure 8. i d r One-means of carryingoutgthe invention is to adjust the oscillator circuitso thatit will oscillate 'ly-eli'minatedto formacurve illustrateqvdiagraini to, the distance betweenC' and D' 'm'ay helsuhfstantially e11'r'n.inated,'.resultingfin a curve soirnefreceived is" between lines llf and" 12 in the'strengths of received signals are plotted as V abscissaanol the strengths .of the resultant signal wiiibemarked A. jAs 'the'receivedjsignal increases By introducing phenomenaofisaturationor of liniitatiorLjQr Otherwise; the distancebetween A V "7 is shown arifoperation diagramcerrespeiidmgte the diagram shovininil igur. 4;

the resultant-signal:being produced whenfthe strength" of'the'receivedisignal isghetween the,

areohtainedbycontrolling-an oscillator circuit hyjflziieans'off the received signal. Forinstance;

i 7 hand,. the oscillationsmight be 7 setup aitefthe received signals' have erkceed'ed 50 only when the oscillator tube is operating on-zthe straight portion of its plate+current= grid' voltage curve, a conventional iorxm of: which is shown in Figure- 9," the straight'portionbeingiapproximately between the points25and'26: V j.-

of the oscillator of sufiicient magnitude to bring the bias point between the points 25 and 26, oscil lations will obviously takeiplace, such .oscillaa tions ceasing only upon a decline in such potential below the required magnitude. a

This corresponds to the operation illustrated in Figure 8.

The magnitude of the applied positive potential being a direct function of the received signals,

it follows that if this potential becomes sufiiciently great, the bias point maybe pushed beyond the point 26, whereupon oscillations will cease. V

' Let. us assume'now that the oscillator circuit is adjustedso that the bias point is between the points 25 and figandthe circuit is oscillating when no signal is received. As the received signal increases in strength the bias point is pushed upwardly on the curve and oscillations will cease when the bias point passes beyond the point 26, starting again; of course, when the bias point returns to within points 25 and 26. The, latter corresponds to the diagrain shown in Figure 7.

"Another way of V accomplishing the desired results is to have the received signal impress a negative bias onthe grid of the oscillator tube. In"

this instance, to obtain results corresponding to the diagram of Figure 7,, the bias point would be between the points 25 and '26 when no, signal is received. Then as the strength of the received signal increases the bias point is pushed downwardly on thejcurve in Figure 9 and the oscillations stop when the bias point passes over the curved portion. v

"Ijo obtain the results illustrated in Figure 8 the bias point. would'be adjusted so as to fall above'the pointk26 when no signal is received. Then as the strengthof the received signalincreased the bias point would be pushed downwardly tobetween points 25 and 26, whereupon oscillations would be produced. v p A circuit for purposes ofimpressinga negative potential onthe grid of, an oscillator of a magnitude proportional to the strength of the received signal is illustrated in Figure 10, in which 23 is a detector tube, 29 an oscillatortubashown for'convenience as of the screen grid type,.and 30 isan amplifier or detector tube. Thesignal is received by primary 3! of transformer 32 from any desired source such as directly from the antenna a which maybe a rotating loop as above indicated,

or morepreferable, from a radio-frequency amplifier, or if "desired, from an audio-frequency amplifier connected to a radio-frequency amplifier. One end of secondary 33 is'connect'ed to filament 34 of tube 28, the otherfend is connectedto grid 35, tube 28. A potentiometer 36 for adjusting the bias on grid 35 may be interposed in the grid-filament circuit if desired. A resistance 3? is connected in the output circuit of tube 28, together'with a source of potential shown at 38. A condenser 39 of by-passing dimensions is shown connected across outer: points 40 and 4| of resistance 31. v

Tube 29 comprises filament 42, 'screen grid 43,-control grid 44, and plate55. Point 4| is connected to control grid 44 through an oscillatory circuit 45 having a condenser 46 and a coil 41. Coil' li is coupled toithe plate circuit of tube 29 through coil 48. Screen grid ASfis' connected to the plate circuit as shown at 9; the grid 43 .mary winding 3!. across resistance 31, which in turn increases the and plate 45 being connected to the filament 42 through a source of potential 50, made adjustable'asindicated-at EI.

Grid 53 of tube 30 is connected to point 54 "ofithe plate circuit. of tube 29 through condenser 55, and to filament 56 of tube 30 through resistance 51. [A translating device 58 is shown in the output circuit of 'tube 3fl.

The-operation of the form of the invention shownin Figure 10 is as follows: Oscillations are produced byadjusting tap and the coupling between coils 47 and 28 when no signals are received in primary 3 I. These oscillations are produced'in spite of the negative bias on grid M produced by the drop across resistance 31 in the plate circuit 'of tube 28. Tube 28, operating'as a detector on thelowerportion of its plate-cur-.'

rent"'grid-voltage curve, causes anincreasein its platecurrentupon a flow of current in pri- This increases the'RI drop where the drop across resistance 31 is not ,suificient to prevent oscillation of tube 2'9.'

Let us assume now that thejbias on grid 44 is such as to bring the'bia's point above point 26 onthe. curve in Figure 9. The tube 29 would not'oscillate in this instance untilhthe current received at 3| is of sufficient magnitude to bring the bias point down between points 25 -and. 26.

, The circuit for the purpose of impressing a positive potential on the grid of an oscillator of a magnitude proportional to the strength of the received signal is illustrated in Figure 11. This circuit is in all respects similar to the circuit shown in Figure except that, whereas "the point 40 of resistance 37 is still directly connected (in this instance shown through battery 63) tofthe filament 42, the point 4! is not directly connected to the plate of tube 28 but is directly connected to the, filament 34 thereon The filament 35 is heated froina separate source, shown at 50. .Plate fil of tube 28 is connected directly tothe potential source 50 by an adjustable means illustratedatfil I I A C battery, illustrated at.63, may be, connected as shown for thelfpurposejof placing a negative bias on the gridf lt.

The operation of the circuit shown in Figure 11 is as follows: The current flowing normally through resistance 31 causes a positive potential to be applied on the grid 44'. As'the current in winding 3! increases this positive, potenthe circuit would be adjusted so as not to oscil-' late with no current inwinding 3l, that is, the bias point would be below point on the curve.

Upon increasing the current in winding 3|, the

the sensitiveness of the circuitis materiallyincreased in viewof the fact that the straight porreceivers 58.

bias point would be pushed upwardly on the curve and when between points 25 and 26 the circuit would begin to oscillate. It is of course understood that if the current in winding 3! increased to such an extent as to push the operation above point 26 the circuitwould cease to oscillate;

Furthermore, should the signals be of sufli tion of thegrid-voltage plate-cur'rentcurve has a greater slope for a screen grid tube. Therefore it requires only smalldifierences in potential between points 40 and M to cause tube 29 to oscillate or cease oscillating or to oscillate with maximum amplitude, thus conforming to the :op-

eration illustrated inFigures i andG; j However, it is to be strictly understood tube illustrated at 29, in which case the screen grid 43 and its connection to the source of 'potential 50 would be eliminated, the connections otherwise being identical. i

junctions cooperates With-the resistance 51 to place the proper bias on grid 53, so that the tube 30 will operate as an amplifier upon the straight portion of its grid-voltage plate-current curve,

I or to cause tube 30 to operate as a detector.

The oscillations may beeither of audio-or. of radio-frequency. If of the audio-frequency, tube 30 or its equivalent merelyacts as an amplifier for the purposes of operating translating mechanism shown conventionally as a pair of head If the oscillations are of radio-frequency it is possible to adjust the frequency thereof so as to produce with the received alternations a heterodyne note in which case the tube 30 or its equivalent would act as'a detector. 7 v i Inasmuch as the timevconstant of the oscillatory circuit is a function of the frequency thereof in the event'of rapidly intermittent received signals, it might be necessary to increase thefrequency .of the oscillatory circuit to in turn 'decrease its time constant so as to be able to follow the received signals. i

It is of course understood that the oscillatory circuit may beernployed to control any other circuit, be it an amplifier ordetector or otherwise, the amplifier 30 and the head phones 58 being shown merely for the purposes of illustration.

The invention comprises broadly the starting orstopping of oscillations in the oscillatory circuit by means of a change in flow of current in a circuit coupled to the oscillatory circuit, said flow of current being in turn controlled by'th strength of the received signals.-

. The particular description herein is given merely. for the purposes of illustration and withthat a three-electrode'tube might be used in place of the Having described the invention, it is obvious that many modifications may be made in the same within the scope of the claims without departing from the spirit thereof. I claim: v

1. Apparatus for determining the maxima or minima of reception of electromagnetic waves, comprising in combination, a vacuum tube detector, an antenna for receiving said waves coupled to the input of said detector, a resistance connected in the output circuit of said detector in such a manner that the plate current from' said detector flowing through said resistance pro- [duces a potential drop thereacross proportional to the strength of the signals impressed upon the input of said detector, a tetrode vacuum tube oscillator comprising a cathode and a control grid, an oscillation circuit comprising a tuning' condenser and a coil connected in parallel, said oscillation circuit being connected in'series between one side of said resistance and the control grid of said tetrode vacuum tube oscillator, the other side of said resistance being connected to the cathode of said oscillatorwhereby the potential drop across said resistance is impressed upon the control grid of said vacuum tube oscillator to control the oscillations therein, and means for indicating the generation of oscillacontrol grid, a plate, and a positively biased tions by said oscillator, whereby a resultant sigscreen grid located between said cathode and said control grid for preventing any back radiation of oscillations into said detector, circuit means for connecting the output of said detector to the input of said oscillation generator whereby'the oscillations of. said generator are controlled in accordance with the signals received in said antenna circuit, andtranslating means for audibly cathode and electricallyconnected to said anode circuit so that it operates at the same potential as said anode and prevents feed back of oscilla tions into said detector circuit, a' control grid positioned between said screengrid and said anode for controlling the oscillations in said oscillation generator tube, a circuit connecting the outputof said detector tube to the input of said oscillator tube, said circuit including a resistance one side of which is connected to the control grid of said oscillator and the other side connected to the cathode of said oscillator, whereby the potential drop across said resistance caused by the plate current of said detector tube .fiowing' through said resistance is impressed upon the 'control grid of said oscillator, a triode vacuum tube connected to the output of said oscillation generator for amplifying'the output thereof, and translating means connected to the output of said amplifier for indicating said amplified oscillations. i V I JEAN ROGER GEORGES J ULES BLANCARD. i 

